Mikado High School trains the best students to be the best mercenary bodyguards. But Morito Hayama, a merc escort student with no rank whatsoever, is suddenly assigned to guard a person so highly valued that no escort has ever survived before. Will his subject survive the experience? Will HE survive?!

From MangaHelpers:
One day in the 21st century, a gate opened in the middle of the Ginza district of Tokyo. Out of the gate poured soldiers and strange creatures, and they soon made Ginza look like an image of hell. The gate apparently connected Japan to another world, a world with a militant empire and many supernatural creatures. The Japanese Self-Defense Force decided to send a small group, ...

There are three series of Baki, this one is Grappler Baki, the 1st one.
1-Grappler Baki(1991-1999) 42 volumes
2-New Grappler Baki(1999-2005) 31 volumes
3-Hanma Baki: Son of Ogre(2005-12-05) ? volumes
"To be the strongest in the world!" That is Baki Hanma's dream. The mysterious, young, martial artist aspires to follow in his sinister father's footsteps as the world's strongest crea...

Summary translated from the back cover:
The stage is set in the prestigious Private Joshi (girls) Oka High School — or more commonly known as Joshi High. It became co-educational a few years ago, but females still heavily outnumber the males. The number of males could be easily counted. While one would think males would be pampered in such a harem school, the reality is far from being heavenly....

Oe Kintarou is a Tokyo University Law School dropout. However, he had completed all the course work needed to graduate before leaving school. Since then, he has wandered through many jobs all over Japan as a student of life with little more than a journal, a pen, and his trusty mountain bike (the Mikazuki 5). On his journeys, he runs into various compromising situations with beautiful women, and h...

Somewhere in Tokyo, there is a room. In that room is a black sphere. Periodically, people who should otherwise have died are transferred to the room. There, the sphere gives them special suits and weapons, and sends them out on a mission to kill aliens here on Earth. While these missions take place, the rest of the world is largely oblivious to them. These missions are lethal--few participants sur...

Bronte is running away from a failed wedding ceremony in the rain when she finds a cabin for shelter, occupied by a blood-soaked man with Gold eyes, who claims he just killed a man. His name is Mars West, and on impulse he kisses her, just as the police come to drag him away.
Five years later Bronte comes to New York to see Mars, who spent three years in prison for the murder it turns out he di...

Last Order begins when Alita is resurrected by Desty Nova's nanotechnology in the floating city of Tiphares. The city's dark secrets are brutally exposed, but it turns out to be a small part of a complex world. Going into space with new and old companions alike, to look for her lost friend Lou Collins and to find out more about her forgotten past, Alita is caught up in an interplanetary struggle b...

A test type Zoanoid escapes from the Kronos Corporation with three Guyver Units. Kronos soldiers attempt to recover the units from the test type, but are thwarted when the test type detonates a bomb that he has concealed in his bag. The Guyver Units are scattered in the blast. Two young high school students, Sh? Fukamachi and Tetsur? Segawa, stumble across a lost Guyver Unit known as "Unit I&...

Taking place in a four year period, the story centers on two young women, 19-year old Irene "Rally" Vincent and her partner, 17-year old "Minnie" May Hopkins.
Rally and May operate the titular "Gunsmith Cats" gunshop in Chicago, Illinois. Rally also works as a bounty hunter, assisted by May, which is the impetus behind many of the stories.
From Baka-Updates:
Gi...

"Casio and his little sister Nokia both work as bounty hunters who use magic packets that they download through their mobile phones and cast with the built-in camera to defeat mysterious apparitions called phantasms. The bounties for these phantasms are quite high, but the enormous fees for the magic packets they download and the property damage they create has reduced them to a homeless stat...

A wounded soldier with a disturbed mind kidnaps the priest who tries to help him. He then has the brilliant idea of going AWOL with the priest. He's in the middle of the African desert in WWII, with supplies running low and his sanity (or is it his morality?) long gone. All that's left is sex and agony. And maybe, eventually, death.

Oshino Makoto just started as a temporary teacher at an all girls academy where he finds his childhood sweetheart working as a teacher.
Can his rekindled love survive the onslaught of sexy students begging Makoto to rescue them from the schemes of perverted teachers?
From Baka-Updates:
Gakuen Heaven is the story of Oshino Makoto in his attempt to become a teacher, in order to fulfill a prom...

Sakura Keita, a university student, is in dire straits when he drops a graph critical to passing his class. However, he is rescued by his fellow student, Kurimiya Honoka, who manages to recover it for him. The two hit it off immediately, but will Keita really be able to hold on to his dream girl?

A rather morbid, sombre manga about two high school students, Kamiyama Itsuki and Morino Yoru, who have a peculiar interest in deaths and especially in murders that are committed near to them. Due to their strong fascination with murder and highly-developed analytical skills(along with some luck), they manage to solve the murders that have even eluded the authorities. However, acting on their own ...

Summary from ANN:
It is panic at the Kuron institute : a guinea-pig escaped. And not any guinea-pig : it is Elaine, a fourteen year old girl, endowed with immense powers. Her father, the professor Reed, tried on her an operation aiming at giving her a psychic force equivalent with that of a nuclear fission. Elaine has a twin sister, Diana, resulting from the same experimentation. Both developed...

The Biblical story of the Genesis, revised and depicted with the usual unholy irony of Kago, with delirious situations quickly following one after another.
The story is from the collection called Kasutoru Shiki.

Kyotaro is just an ordinary guy trying to lead an ordinary high school life despite the fact that he is the son of a Yakuza boss. Then comes Kumiko, his half-sister he's never met before, who's looking for a man with a centipede tattoo who killed her loved ones in the past. Will Kumiko and Kyotaro be able to manage their family business? Will Kumiko ever find and avenge the man with the centipede ...

From ShoujoMagic:
This manga is loosely based on The Tale of Genji / ??????(Genji Monogatari) and is a MUST read!
When the Emperor takes a new Empress, she is barely older than the Emperor's son Hikaru. She becomes both the one woman Hikaru loves and the one woman he can never have. And so Hikaru's feelings roam as his body wanders from bed to bed, seeking a replacement for her. When he find...